全文获取类型
收费全文 | 3761篇 |
免费 | 273篇 |
国内免费 | 5篇 |
出版年
2023年 | 9篇 |
2022年 | 21篇 |
2021年 | 48篇 |
2020年 | 27篇 |
2019年 | 32篇 |
2018年 | 54篇 |
2017年 | 31篇 |
2016年 | 64篇 |
2015年 | 128篇 |
2014年 | 163篇 |
2013年 | 220篇 |
2012年 | 259篇 |
2011年 | 254篇 |
2010年 | 161篇 |
2009年 | 161篇 |
2008年 | 234篇 |
2007年 | 261篇 |
2006年 | 243篇 |
2005年 | 271篇 |
2004年 | 231篇 |
2003年 | 200篇 |
2002年 | 204篇 |
2001年 | 32篇 |
2000年 | 37篇 |
1999年 | 54篇 |
1998年 | 60篇 |
1997年 | 35篇 |
1996年 | 37篇 |
1995年 | 35篇 |
1994年 | 41篇 |
1993年 | 27篇 |
1992年 | 25篇 |
1991年 | 36篇 |
1990年 | 31篇 |
1989年 | 20篇 |
1988年 | 32篇 |
1987年 | 14篇 |
1986年 | 11篇 |
1985年 | 26篇 |
1984年 | 20篇 |
1983年 | 15篇 |
1982年 | 16篇 |
1981年 | 33篇 |
1980年 | 21篇 |
1979年 | 17篇 |
1978年 | 18篇 |
1977年 | 8篇 |
1976年 | 8篇 |
1975年 | 15篇 |
1971年 | 6篇 |
排序方式: 共有4039条查询结果,搜索用时 187 毫秒
11.
Kiyotaka Chinzei Kantaro Fujioka Hiroshi Kitazato Itaru Koizumi Tadamichi Oba Motoyoshi Oda Hisatake Okada Toyosaburo Sakai Yoshihiro Tanimura 《Marine Micropaleontology》1987,11(4)
Downcore changes in microfossil assemblages and oxygen isotope ratios in three piston cores recovered from the Northwestern Pacific, off central Japan, show that the subtropical Kuroshio front was located to the south of C-4 core site (Lat. 33° N) during the last glacial. The front then advanced northward, passing over the C-4 site and the C-6 site (34.6° N) at about 13 ka and 10 ka, respectively, and reached the C-1 core site (36° N) at about 7 ka. After 5.5 ka it retreated to the area between the C-1 and C-6 sites. A brief but significant cold event, the readvance of the cold Oyashio Current, is recognized between 11 and 10 ka in the two northern cores, but the current did not reach the southern C-4 site. A contemporaneous cold event is known in the North Atlantic, and the cooling was probably a global phenomenon likely to be associated with lowering of sea level. Contamination of isotopically light water is apparent between 14 and 11 ka in the marked change in isotopic composition of benthic foraminifers. Oxygen isotope ratios of planktonic foraminifers show that prior to the advance of the Kuroshio front, the surface water at these core sites was isotopically lighter than the Kuroshio water at that time. 相似文献
12.
Yasuaki Kagotani Setsuji Hisano Yoshihiro Tsuruo Shigeo Daikoku Yasuhiko Okimura Kazuo Chihara 《Cell and tissue research》1990,262(1):47-52
Summary Certain populations of arginine vasopressin (AVP) neurons in the magnocellular paraventricular nucleus became immunoreactive for neuropeptide Y (NPY) when rats were treated with colchicine or monosodium glutamate (MSG). The co-storage of these peptides was examined by empooying a post-embedding electron-microscopic immunohistochemistry technique using goldlabeled antibodies to the two peptides. In colchicinetreated rats, the neuronal perikarya contained numerous secretory granules showing co-storage of the two peptides. The cells of the MSG-treated rats were characterized by having well-developed Golgi bodies with the granular structures also co-storing the two peptides, although the secretory granules in the perikarya were rather fewer than in the colchicine-treated rats. It is concluded that the destruction of the arcuate nucleus by MSG-treatment may potentiate the synthesis of NPY in AVP neurons, the synthesis of which is latent in intact animals. 相似文献
13.
The subcellular distribution of beta-glucuronidase acquired by deficient human fibroblasts during co-culture with peritoneal macrophages was compared with that taken up by receptor-mediated endocytosis. Labelled enzyme taken up via receptors was located initially in a low-density endosomal fraction and was transferred to lysosomes within a few minutes. The beta-glucuronidase acquired during 24 h of co-culture was present almost entirely within lysosomes and had a distribution profile identical with that of endogenous beta-hexosaminidase. Monensin prevented transfer of radiolabelled enzyme from endosomes to lysosomes and had a similar effect on the distribution of enzyme acquired by direct transfer, causing beta-glucuronidase to accumulate within endosomes. When the temperature was lowered from 37 degrees C to 19 degrees C, the rate of transfer of enzyme from endosomes to lysosomes was decreased during both direct transfer and indirect receptor-mediated endocytosis. These results show that a lysosomal enzyme acquired by direct transfer during cell-to-cell contact follows a similar intracellular route and has a similar distribution to that of enzymes taken up via cell-surface receptors. 相似文献
14.
Yoshihiro Akimoto Akiko Obinata Hiroyoshi Endo Professor Hiroshi Hirano 《Cell and tissue research》1988,254(3):481-485
Summary The effect of epidermal growth factor (EGF) on the basement membrane structure of chick embryonic skin cultured in a chemically defined medium (BGJb) containing 20 mM hydrocortisone, and EGF at 10, 50, or 100 ng/ml supplemented with 5% delipidized fetal calf serum, was examined by electron microscopy. During development of the epidermis in vitro, EGF (100 ng/ml) caused striking changes to occur in the basement membrane structure and in the keratinization process. The basement membrane frequently became discontinuous with many gaps apparent in section, and occasionally became folded following detachment from the basal surface of the epidermis and protruded into the underlying dermis. In the basal and intermediate cells of EGF-treated epidermis, tonofilament bundles were decreased in number, while desmosomes and hemidesmosomes revealed no significant changes in morphology. 相似文献
15.
Sueyoshi Kuni; Kubo Yoshihiro; Yamagishi Kenji; Ogura Nagao; Ochiai Kuniyasu; Fukushima Kazuo; Ikeda Tadashi; Nakagawa Hiroki 《Plant & cell physiology》1988,29(6):975-980
Two monoclonal antibodies, 17(3)9 and 36(79)4, were preparedagainst nitrate reductase from Spinacia oleracea L. leaves.An enzyme-linked immunosorbent assay showed that 17(3)9, butnot 36(79)4, reacted more strongly to heat-denatured than nativeantigen. These antibodies inhibited NADH-nitrate reductase aswell as its various partial activities including reduced methylvilogen-nitrate reductase, reduced flavin mononucleotide-nitratereductase and NADH-cytochrome c reductase activities, but notNADH-ferricyanide reductase activity. Immunoblotting after electrophoreticseparation of nitrate reductase fragments obtained by Staphyrococcusaureus V8 protease digestion of native enzyme revealed thatthe two monoclonal antibodies bind to different epitopes locatedon the 28 kDa of the NADH-ferricyanide reductase domain. (Received October 2, 1987; Accepted June 9, 1988) 相似文献
16.
Shuzo Miyamoto Yoshihiro Matsuda Shin-ichiro Sano Hiroshi Shiraki Hachro Nakagawa 《Neurochemical research》1992,17(7):723-727
The activity of ammoniagenesis from guanine nucleotides was found to increase significantly in rat brain after infusion of kainic acid into the striatum. Among the enzymes involved in degrading guanine nucleotides, nucleoside diphosphatase was markedly increased in the lesioned striatum. The enzyme activity began to increase 2 days after the infusion, and reached the maximum on the 13th day, the level being 4 times as high as that of the intact contralateral region. The increased activity was due to Type L enzyme, judging from its substrate specificity. Puromycin and cycloheximide inhibited this increase, indicating that the increased activity resulted from an increase in the net synthesis of the enzyme. These findings suggest that Type L NDPase might play some important roles in gliosis after neuronal lesion. 相似文献
17.
Gyu-Chul Hwang Yoshihiro Ochiai Shugo Watabe Kanehisa Hashimoto 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1991,161(2):141-146
Summary Heavy meromyosin subfragment-1 (S1) was prepared by -chymotrypsin from myosin of carp acclimated to either 10°C or 30°C for a minimum of 5 weeks. The objective of these studies was to document thermally-induced changes in the myosin molecule and to extend previous observations. Ca2+- and K+ (EDTA)-ATPase activities of cold-acclimated carp S1 were 1.1 and 0.8 mol Pi·min-1·mg-1, respectively, and these values did not differ significantly from those of warm-acclimated carp. The inactivation rate constant (KD) of S1 from cold-acclimated carp was 32.1x10-4· s-1, compared to 13.2x10-4·s-1 for warm-acclimated carp. The maximum initial velocity of acto-S1 Mg2+-ATPase activity at pH 7.0 in 0.05 M KCl was 9.3 s-1 with cold-acclimated carp, about 3.7 times higher than that for warm-acclimated carp. However, no significant difference was observed in the apparent affinity of S1 to actin. Peptides maps of the heavy chain of S1 were different and suggested distinct isoforms for the myosins from warm- and cold-acclimated muscle.Abbreviations
ATPase
adenosine 5-triphosphatase
-
DTNB
5,5-dithiobis (2-nitrobenzoic acid)
-
DTT
dithiothreitol
-
EDTA
ethylenediaminetetraacetic acid
-
EGTA
ethyleneglycol bis (-aminoethylether)-N,N,N,N-tetraacetic acid
-
K
D
inactivation rate constant
-
K
m
apparent dissociation constant
-
P
i
inorganic -phosphate
-
PMSF
phenylmethane-sulfonyl fluoride
-
S
1
heavy meromyosin subfragment-1
-
SDS
sodium dodecyl sulfate
-
SDS-PAGE
SDS-polyacrylamide gel electrophoresis
-
TPCK
N-tosyl-l-phenylalanyl chloromethyl ketone
-
V
max
maximum initial velocity 相似文献
18.
Yoshihiro Toh Akiko Mizutani Fuminori Tokunaga Tatsushi Muta Sadaaki Iwanaga 《Cell and tissue research》1991,266(1):137-147
Summary The structure of hemocytes in the normal state and during blood coagulation, and the intracellular localization of three clotting factors and two antimicrobial factors were examined in the Japanese horseshoe crabTachypleus tridentatus. Two types of hemocytes were found in the circulating blood: non-granular and granular hemocytes. The latter contained numerous dense granules classed into two major types: L- and D-granules. The L-granules were larger (up to 1.5 m in diameter) and less electron-dense than the D-granules (less than 0.6 m in diameter). The L-granules contained three clotting factors and one antimicrobial factor, whereas the D-granules exclusively contained the other antimicrobial factor. After treatment with endotoxin, the L-granules were released more rapidly than the D-granules, although almost all granules were finally exocytosed. The granular hemocyte possessed a single Golgi complex; possible precursor granules of L-granules and D-granules contained tubular and condensed dense material, respectively. These data are discussed in relation to the self-defense mechanisms of the horseshoe crab. 相似文献
19.
Yoshihiro Mogami Hans Machemer 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1991,168(6):687-695
Summary Motor responses of cirri (= organelles consisting of bundles of cilia) in the protozoan Stylonychia are elicited by positive or negative shifts of the membrane voltage from its resting state. The same responses are evoked at voltages near the Ca2+ equilibrium potential (ECa) applying extremely positive steps under voltage clamp. Motor responses recorded at large positive voltages approaching ECa from the negative side corresponded to cirral activation following physiological depolarization from the resting potential (DCA). The hyperpolarization-induced activation of the cirri (HCA) was documented during step potentials positive to ECa, suggesting that the observed HCA of the cirri resulted from an efflux of Ca2+ from the ciliary space as compared with DCA, which is related to Ca2+ influx. The ciliary responses were graded functions of the rising outward or inward driving force for Ca2+. Slopes of reciprocal plots of response latencies near ECa as a function of membrane potential indicate a removal of Ca2+ during HCA which exceeds the free intraciliary Ca2+ content at rest. It is suggested that this excess Ca2+ is released from axonemal binding sites. 相似文献
20.
Sequence of EndoA gene encoding mouse cytokeratin and its methylation state in the CpG-rich region. 总被引:3,自引:0,他引:3
A genomic clone obtained from mouse liver DNA using a mouse cytokeratin EndoA cDNA probe revealed the complete sequence of the EndoA gene. The gene is divided into nine exons and the exon-intron pattern has been conserved compared to that of other type-II cytokeratin-encoding genes. The 5' upstream, 3' downstream and first and third introns contain potential regulatory sequences, including polyoma virus enhancer motifs (PEA1 and PEA3) and AP-1 elements. The 5' regions upstream of the EndoA, EndoB and Ck8 genes contain homologous sequences surrounding the TATA boxes. In addition, a CpG dinucleotide cluster region was located around the first exon. This CpG cluster region was found to be hypomethylated in endodermal PYS-2 cells, retinoic acid-treated F9 cells, and F9 embryonal carcinoma cells, but hypermethylated in BALB/C 3T3 fibroblast cells that do not express EndoA. These findings may provide a clue to understanding the molecular mechanisms of EndoA gene expression. 相似文献